ANLTR4 Cpp demo fails to run because of a __gthread problem

Question

I have compiled ANTLR4 runtime in a VirtualBox Ubuntu 20.04, with g++ 9.4.0.

I want to learn how to integrate the ANTLR tool into a Cpp project, So I compiled the antlr4 runtime with demo. The compilation was sucessfull, but when I try to run the built elf file. The following error occurs, the error occurs at the initialization of the Lexer. it seems that __gthread is not started.

Breakpoint 1, main () at /home/zhao/Downloads/antlr4/runtime/Cpp/demo/Linux/main.cpp:22
22  int main(int , const char **) {
(gdb) n
23    ANTLRInputStream input(u8" =  + \"\";(((x * π))) * µ + ∰; a + (x * (y ? 0 : 1) + z);");
(gdb) n
24    TLexer lexer(&input);
(gdb) s
antlrcpptest::TLexer::TLexer (this=0x7fffffffdb20, input=0x7fffffffda50) at /home/zhao/Downloads/antlr4/runtime/Cpp/demo/generated/TLexer.cpp:171
171 TLexer::TLexer(CharStream *input) : Lexer(input) {
(gdb) n
172   TLexer::initialize();
(gdb) s
antlrcpptest::TLexer::initialize () at /home/zhao/Downloads/antlr4/runtime/Cpp/demo/generated/TLexer.cpp:272
272 void TLexer::initialize() {
(gdb) s
273   std::call_once(tlexerLexerOnceFlag, tlexerLexerInitialize);
(gdb) s
std::call_once<void (&)()> (__once=..., __f=@0x7fffffffda00: {void (void)} 0x7fffffffda00) at /usr/include/c++/9/mutex:666
666     call_once(once_flag& __once, _Callable&& __f, _Args&&... __args)
(gdb) s
670       auto __callable = [&] {
(gdb) 
675       __once_callable = std::__addressof(__callable); // NOLINT: PR 82481
(gdb) 
std::__addressof<std::call_once<void (&)()>(std::once_flag&, void (&)())::{lambda()#1}>(void (&)()) (__r=...) at /usr/include/c++/9/bits/move.h:47
47      __addressof(_Tp& __r) _GLIBCXX_NOEXCEPT
(gdb) 
48      { return __builtin_addressof(__r); }
(gdb) 
std::call_once<void (&)()> (__once=..., __f=@0x55555556b4c3: {void (void)} 0x55555556b4c3 <(anonymous namespace)::tlexerLexerInitialize()>)
    at /usr/include/c++/9/mutex:675
675       __once_callable = std::__addressof(__callable); // NOLINT: PR 82481
(gdb) 
676       __once_call = []{ (*(decltype(__callable)*)__once_callable)(); };
(gdb) 
std::call_once<void (&)()>(std::once_flag&, void (&)())::{lambda()#2}::operator void (*)()() const (this=0x7fffffffda00) at /usr/include/c++/9/mutex:676
676       __once_call = []{ (*(decltype(__callable)*)__once_callable)(); };
(gdb) 
std::call_once<void (&)()> (__once=..., __f=@0x55555556b4c3: {void (void)} 0x55555556b4c3 <(anonymous namespace)::tlexerLexerInitialize()>)
    at /usr/include/c++/9/mutex:683
683       int __e = __gthread_once(&__once._M_once, &__once_proxy);
(gdb) 
__gthread_once (__once=0x5555556e32bc <(anonymous namespace)::tlexerLexerOnceFlag>, __func=0x7ffff7eabc20 <__once_proxy>)
    at /usr/include/x86_64-linux-gnu/c++/9/bits/gthr-default.h:699
699   if (__gthread_active_p ())
(gdb) s
__gthread_active_p () at /usr/include/x86_64-linux-gnu/c++/9/bits/gthr-default.h:252
252   return __gthread_active_ptr != 0;
(gdb) display __gthread_active_ptr
1: __gthread_active_ptr = (void * const) 0x0
(gdb) n
253 }
1: __gthread_active_ptr = (void * const) 0x0
(gdb) n
__gthread_once (__once=0x5555556e32bc <(anonymous namespace)::tlexerLexerOnceFlag>, __func=0x7ffff7eabc20 <__once_proxy>)
    at /usr/include/x86_64-linux-gnu/c++/9/bits/gthr-default.h:699
699   if (__gthread_active_p ())
1: __gthread_active_ptr = (void * const) 0x0
(gdb) n
702     return -1;
1: __gthread_active_ptr = (void * const) 0x0
(gdb) n
703 }
1: __gthread_active_ptr = (void * const) 0x0
(gdb) n
std::call_once<void (&)()> (__once=..., __f=@0x55555556b4c3: {void (void)} 0x55555556b4c3 <(anonymous namespace)::tlexerLexerInitialize()>)
    at /usr/include/c++/9/mutex:690
690       if (__e)
1: __gthread_active_ptr = (void * const) 0x0
(gdb) n
691     __throw_system_error(__e);

I tried looking up in the CMakeLists but cannot find where the gthread package is linked. Besides, I am using a newly installed ubuntu 20.04. If it is a dependency issue please tell me which package to install.

Thank you! Best Zhao

score 0 · Answer 1 · answered Sep 05 '22 at 15:07

I had the same issue when I updated the ANTLR4 version used in my project but I just added

find_package(Threads REQUIRED)
target_link_libraries(MyTarget Threads::Threads)

to the CMakeLists.txt file of my project, where MyTarget is the name of the library or executable where I'm linking the antlr4 library.

Better explanations here and here. Hope this helps you too!

JustAnotherComputerScientist · Accepted Answer · 2022-10-12T21:34:08.010

So I had this same problem and all I could find online was a suggestion to add

find_package(Threads REQUIRED)
target_link_libraries(MyTarget Threads::Threads)

to the Cmake files. However, I soon realised that this solution had already been implemented as part of a patch pushed earlier in the year, but the issue was not resolved for me...

What was actually needed in my case was to set the cmake variable THREADS_PREFER_PTHREAD_FLAG to ON i.e. set(THREADS_PREFER_PTHREAD_FLAG ON). By doing this, Cmake will pass the flag -pthread to the compiler and linker instead of -lpthread. This solved all my issues.

Full breakdown to build Cpp runtime and demo with -pthread flag

Assuming you already have antlr4 installed using apt (or built manually), using the command line, go to your desired directory and clone the antlr4 repository (if you haven't already done so):

git clone https://github.com/antlr/antlr4.git

Now generate all the lexer and parser files need for the demo as follows:

cd antlr4/runtime/Cpp/demo
antlr4 -Dlanguage=Cpp -listener -visitor -o generated/ -package antlrcpptest TLexer.g4 TParser.g4
cd ..

This will create multiple files and store them in demo/generated/.

From the <antlr4-dir>/runtime/Cpp directory, where <antlr4-dir> is the location you cloned the git repository, edit both CMakeLists.txt and demo/CMakeLists.txt adding

set(THREADS_PREFER_PTHREAD_FLAG ON)

to both files and save.

Back to the command line, from location <antlr4-dir>/runtime/Cpp

mkdir build && mkdir run && cd build
whereis antlr4

the whereis command will result in the location of the antlr4 package you installed through apt (or manually installed). Lets say this location is <apt_loc_antlr4>/antlr4, where <apt_loc_antlr4> is a location on your machine. You will need to substitute this location in the next command:

cmake .. -DANTLR_JAR_LOCATION=<apt_loc_antlr4>/antlr4 -DCMAKE_CXX_STANDARD=17 -DWITH_DEMO=True
make

Assuming all the above worked, you should now be able to run the demo.

cd demo/
./antlr4-demo

ANLTR4 Cpp demo fails to run because of a __gthread problem

2 Answers2